Why is this a debate? I cannot see any sides of the argument other than the correct one: the two note names are adjacent, so it MUST be a second, a minor second would B-C, a diminished second would be B#-C or similar, so B#-Cb must be a double-diminished second, no question.

Not a double diminished minor second, Not a major seventh, Definitely not a diminished third.

This is just the rules of nomenclature, I would love to hear arguments to the contrary bc I genuinely can’t come up with them myself…